Nanoscale Structure of the Liquid–Gas Interphase Surface and the Capillary Fluctuations
D. I. Zhukhovitskii
Joint Institute of High Temperatures,
Russian Academy of Sciences,
Izhorskaya ul. 13, Bd. 2, Moscow, 125412 Russia
Abstract—The nanoscale structure of the liquid–gas boundary layer can be clearly resolved if liquid particles are properly classified. Three particle types are introduced: the internal particles, surface particles, and virtual chains of particles. Then thermal fluctuations of a surface passing through the surface particles can be treated as the capillary fluctuations. The liquid–gas interface was simulated by the surface of a large Lennard-Jones liquid cluster studied using molecular dynamics. One-dimensional averaged slice spectra of the cluster surface in the wave number space that define the surface form are calculated. The frequency Fourier spectrum shows overdamped system behavior, which is the evidence for absence of thermal capillary waves (but presence of the fluctuations) for clusters comprising less than 100000 particles. The time-averaged cluster density profile is given by an error function with the width parameter diverging as the logarithm of cluster size. The linear capillary approach leads to a satisfactory agreement with simulation results.